Hydrogen fluoride treatment of coking and cracking feed stock



Oct. 30, 1962 K. H. MORI-rz ETAL 3,061,539

HYDEOGEN ELuoRTDE TREATMENT oF coxme AND cEAcKING FEED sTocE Glen PorterHamner www@ Potent Attorney Oct 30, 1962 K. H. MORITZ ETAL 3,061,539

HYDROGEN FLUORIDE TREATMENT OF COKING AND CRACKING FEED STOCK T arstenHerber'r Moritz Glen porter Homner Inventors www Patent Atorny UnitedStates Patent Oiitice 3,061,539 Patented Oct. 30, 1962 @0615539 HYDRGGENFLUGRIDE TREATMENT F CGKENG AND CRACKENG FEED STOCK Karsten HerbertMoritz and Glen Porter Hammer, Baton Rouge, La., assignors to EssoResearch and Engineering Company, a corporation of Delaware Filed May25, 1960, Ser. No. 31,625 12 Claims. (Ci. 208-90) This invention relatesto the conversion of hydrocarbons and more particularly relates to theconversion of high boiling hydrocarbons to lower boiling hydrocarbons.

In the catalytic cracking of hydrocarbons it is known that metalcontaminants such as compounds of iron, nickel, vanadium etc. in verysmall concentrations in the oil feed lead to poisoning or contaminationof the cracking catalyst with a decrease in yield of desired productsand an increase in gas and coke yields. This is true if the gas oil isderived by fractionation from a crude petroleum oil or if it is derivedby coking a residual oil.

No satisfactory method has heretofore been disclosed for removingmetallic contaminants from the oil cracking feed stock. The removal ofcontaminants is largely unaffected by conventional desalting techniques,solvent extraction, chemical :treatments and other methods heretoforeproposed.

According to the present invention coker oil feeds such as residual oilsare treated with aqueous and/or anhydrous hydrofluoric acid or hydrogeniluoride and the sotreated residual oil is passed to a coking unit toobtain f 4higher yields of low metals gas oils for use in catalyticcracking than would be obtained by coking alone without the hydrouoricacid treatment.

Normally, catalytic cracking feedstocks are limited by two qualityspecifications: Conradson carbon and metals content. rllhe Conradsoncarbon specification will vary from unit to unit, but because `of carbonburning limitations a catalytic` cracker can tolerate feeds only up to acertain maximum Conradson carbon. The limitation on metals, especiallynickel, must be met for any catalytic cracking feedstock because metalscontaminate the catalysts.

Coking operations, such 4as iluid coking, are used in reneries where itis desired to upgrade residual feedstocks of high Conradson carbonand/or metals content to provide feedstocks for catalytic 'crackingunits. Fluid coking operations are normally conducted at about 950 to980 F. The products are taken overhead as vapor and normally the heavyportion boiling above i5 F. is recycled to extinction. The Irecycle cutpoints may be lower than 10l5 F. if a gas oil of lower Conradson carbonis desired, but it cannot usually be extended above that temperaturebecause volatile or vapor-ous metal cornpounds of the nickel andvanadium type will be carried over into the product. Thus the metalslevel in the gas oil sets the maximum for the coker recycle cut point.

As the recycle cut point in coking is lowered the product distributiondeteriorates into higher gas and coke make and lower gas oil yields.Thus, where higher Conradson carbon in the gas oil can be tolerated (andthis is often the case, because coker gas oils are usually low inConradson carbon and because in most reiinery situations coker gas oilsare only incremental catalytic cracking feedstocks, so that thepercentage contribution of the coker gas oil Conradson carbon to thetotal pool Conradson carbon is only small) it would be desirable toincrease the recycle cut point to maximize the gas oil yield, or tooperate the Coker completely without recycle. This method of operationhas the additional advantage that higher steam dilutions can be used inthe reactor which 2 has the eect of lowering the per-pass conversion andthus further increases the gas oil yield.

During treatment with hydrofluoric acid, the contaminating volatilemetal compounds are selectively changed to a solid form. After thisconversion, these metal compounds do not vaporize and do not comeoverhead with coker vapors but are deposited on the coke during thecoking step. Because the Coker vapors are substantially free ofcontaminating metals when using the present invention, the entirevaporo-us overhead fro-m the coking reactor in one form of the inventionmay be passed directly to a catalytic cracking unit and in another formof the invention the coker vaporous overhead products may be iirstfractionated to separate a high boiling gas oil fraction which is thenpassed to a catalytic cracking unit.

With ythe present invention, coking is used to crack a hydrogen fluoridetreated residual oil to produce a greater volume of gas oil suitable ascatalytic cracking feedstock than is obtained only by coking without HFpretreatment and, if desired, the entire vaporous overhead crackedproducts from the coker reactor may be passed directly to a catalyticcracking unit without fractionation into several fractions. Theapplication of this invention allows much greater ilexibility in theoperation of the coker, and in addition, the Coker can be operated morecheaply. Operation with limited recycle or completely without recycle,as well as decreased per-pass conversion adds to the flexibility of thecoker. Economic benefits are obtained from operating the coker atminimum or zero recycle because of lower investment and operating costs.

The hydroiluoric acid may be used repeatedly in the process since littleor no acid is consumed by reaction with the oil.

The metals content of any distillate fraction will depend upon the typeand concentration of contaminants in the crude oil from which thefraction was distilled, the boiling range of the fraction, and the:amount of entrainrnent which took place during the distillation of thecrude oil. Heavy gas oils in the range of 900 to 1200" F. distilled fromtypical crudes may contain from about l to about 20 pounds `of metalliccontaminants per 1000 barrels. Residual fractions (1000 R+) and gas oils(900 F. to 1200o F.) derived from crudes which are particularly high incontaminants may contain as much as 200 pounds of metal per 1000barrels.

The treating temperature, the volume of aqueous hydroiluoric acidemployed and the intensity with which the oil and the acid `are mixed incarrying out the process of the invention may be varied considerably. Itis preerred to treat at temperatures between about and about 450 F.,although in some cases temperatures as high as 550 F. may be employed.The temperature employed depends, of course, upon other operatingconditions. The volume of acid employed may range between about 0.01 andabout 2 volumes, preferably 0.1 to 1.0 volume, per volume of oiltreated. ln another form of the invention the residual oil feed istreated with anhydrous hydrogen iiuoride at a temperature between about250 F. and 400 F., preferably between about 300 F. and 350 F., thenwater Washed to remove water soluble salts or compounds, filtered toremove any solids and the resulting oil then coked to produce anincreased yield of demetalized coke. The treated oil before coking canbe separated into an asphaltene fraction which is coked and adeasphalted oil which is a good catalytic cracking feedstocksubstantially free of catalyst contaminating metals.

in the drawing;

FiG. 1 diagrammatically represents one form of apparatus adapted topractice the present invention; and

PEG. 2 diagrammatically represents a modied form of apparatus forpracticing the present invention. l

Referring now to FIG. 1 of the drawing, the reference characterdesignates a line through which the oil to be treated is passed intomixing vessel 12. The oil feed may be a residual petroleum oil or anyother metal containing oil fraction from petroleum, shale, coal or othersources. The residual oil fraction usually boils above about 900 F. Themixing vessel 12 is provided with suitable means (not shown) foragitating or mixing the contents of the vessel and is provided withheating coils and jacketing or other means (not shown) for maintainingthe desired temperature within the mixing vessel 12.

The preferred temperature in the mixing vessel is in the range betweenabout 100 F. and 450 F. It is an important feature of the presentinvention that improved results are obtained at these lower temperaturelevels. Above about 550 F., depending on the concentration of thehydrouoric acid, less satisfactory results are obtained because gas oilfractions normally recovered as catalytic cracking feeds may beconverted to coke (or Conradson carbon material) due to the action ofthe acid at these temperatures.

Aqueous hydrouoric acid in a concentration of about 50% by weight andhigher, or anhydrous hydroiluoric acid, is introduced into the mixingvessel 12 through line 14 and is there mixed with the oil introducedthrough line 10. The aqueous hydrofluoric acid solution may be used in aconcentration between about 50 and 100% by weight. The ratio of acidsolution to oil, that is, the acid dosage is determined by the acidconcentration, the temperature and the contact time and may be betweenabout 1 and 200% by weight, preferably 10 to 100% by weight of the oil.The time of contact within the mixing vessel 12 may vary between about 2and 120 minutes. The pressure in the mixing vessel 12 may be betweenabout 100 and 1800 p.s.i.g. or at a pressure suicient to maintain thehydrofluoric acid in liquid state.

After the oil and acid have been mixed the mixture is passed throughline 18 to the settling vessel 20. The acid is withdrawn from thesettling vessel 20 through line 22 and recycled through line 14 to themixing vessel 12. With certain heavy oil feeds and certain acidconcentrations, the acid phase may be lower in density than the oilphase and in this case will rise to the upper part of the settlingvessel 20. The oil phase, which contains some residual acid and themetals as compounds dispersed as oil-insoluble solids, is passed throughline 24 and pressure release valve 26 to ilash vessel 28 where the acidvapors are flashed overhead and passed through line 30, condenser 32 andcompressor 34 to the mixing vessel 12. The flash vessel 28 may beoperated at any pressure below the operating pressure of settler 20 to,obtain good HF separation by flashing.

The above oil phase, which contains the metal conversion products as anoil-insoluble solid dispersion, is

withdrawn from flash vessel or tower 2S and passed v through line 36without filtration or any solids separation directly to at coking unitin which the reference character 42 designates a coking reactor. Thecoking unit is diagrammatically shown and preferably a fluid coking unitis used. In the case of a iluid coking reactor, the temperature in thecoking reactor 42 is maintained between about 950 F. and 980 F.Superheated steam is introduced into the coking reactor 42 through line44 in an amount between about 20 and 50 lbs. per barrel of oil feed.

Coke particles are Withdrawn from the coking reactor 42 through line 44aand mixed with air introduced through line 46 and the resultingsuspension is introduced into the burner or combustion vessel 4S whereat least part of the coke is burned to raise the temperature of the cokeparticles to between about 100 F. and 250 F. higher than that in thecoking reactor 42. The temperature during burning or combustion in theheater vessel 4S is between about l000 F. and 1200 F. The pressure inthe reactor 42 and heater vessel 4S is between about 10 and 60 p.s.i.g.This invention should not be limited by these coker conditions, sincefor other coking units, such as delayed cokers, other operatingconditions may be applicable.

Hot coke particles are withdrawn from the heater vessel 4S through line52 and returned to the coking reactor 42 in an amount suiicient tomaintain the desired temperature in the reactor 42. Part of the coke iswithdrawn through line 54 as product coke from the process.

The particle size of the lluidized coke particles is between about 30and 600 microns with most of the particles being of an overage sizebetween about and 200 microns. Combustion gases pass overhead from theheater vessel 48 through line 56 and may be passed through heatexchangers or waste heat boilers to recover heat therefrom.

The vaporous products of coking are passed overhead from coker reactor42 through line 58 and the total vaporous overhead product may be passedthrough line 62 to a catalytic cracking unit 64 diagrammatically shownin the drawing. Or the vaporous overhead products passing through line5S may be passed through line 65 into fractionating tower 66 to separatecoker vaporous products into desired fractions. One of these fractionsis a gas oil fraction withdrawn through line 68 as a side stream andthis gas oil fraction is passed to the catalytic cracking unit 64. Agaseous fraction is taken overhead through line 72 and a gasolinefraction is withdrawn as a side stream through line 74. The bottomsfraction is withdrawn through the bottom line 76 and may be recycled tothe coking unit and coking reactor 42, or it may be combined with thegas oil fraction leaving through line 68 and used as incrementalcatalytic cracking feed, or it may be used as a fuel oil.

The catalytic cracking unit 64 is preferably of the uidized catalyticcracking type but other catalytic cracking processes may be used. In theiluid cracking reactors the temperature is maintained between about 890F. and 1000" F., the catalyst to oil ratio is between about 5 and 20 andthe w./hr./w. in the cracking reactor is between about 5 and l2. Thepressure in the cracking reactor is preferably atmospheric but may be ashigh as 75 lbs. p.s.ig. The size of the catalyst particles is betweenabout 20 and microns with most of the particles being between a size ofabout 40 and 70 microns.

The regenerator which forms part of the cracking unit 64 but not shownin the drawing is maintained at a temperature between about 1000 F. andll50 F. and a sufficient amount of the hot regenerated catalyst isrecycled to the reactor to maintain the desired cracking temperaturetherein.

Cracked vapors pass overhead from the cracking unit 64 through line 78and are passed into fractionator 82 wherein the cracked products areseparated into a gaseous fraction which passes overhead fromfractionator 82 through line S4, a gasoline fraction Withdrawn throughtop withdrawal line 86, a gas oil or fuel oil fraction withdrawn throughline 88 and a bottoms fraction withdrawn from the bottom of fractionatorthrough line 92. The bottoms from the fractionator 82 may be at least inpart recycled to the cracking unit 64 through line 94 and may be atleast in part discarded from the system through line 96.

According to this invention, the coker gas oil final boiling pointduring fractionation in tower 66 can be increased substantially withoutcarrying contaminating metal compounds into the gas oil fraction. Oneform of the present invention includes the combination of hydroiluoricacid treating of residual oil and coking of the treated oil. Thiscombination of steps permits a higher end point cut for the gas oilfraction so that a higher yield of gas oil substantially free of thecontaminating metals and lower coke and gas yields are obtained.

The following correlated data give a specic illustration of theadvantages which may be gained by the present invention. The feed to thetluid coking unit is about 925 E+ residium and the temperature of thecoking operation is about 950 F. For the HF treatment about 1 Weight ofaqueous HF of 95% concentration per weight of residium is mixed with theresidium feed at a temperature of about 250 F., a pressure of about 300p.s.i.g. and a time of contact of about 60 minutes. In the table I ppm.means parts per million by Weight.

According to the data in Table I it will be Seen that there is a 50%increase in gas oil yield for doubling the Conradson carbon content ofthe gas oil. The Conradson carbon can be controlled by the degree ofconversion. The higher the conversion, the lower the Conradson carbon ofthe product. The data for this example in Table l, column II, representsthe maximum gas oil yield advantage that can be obtained or gained,because no recycle at all was employed. Lower yields and lower Conradsoncarbon can be obtained by recycling any portion of the cracked feed orby increasing the once-through conversion.

The HF treating of coker feeds allows one-through operation which isimpossible because of metals contamination in operation without HFtreating. Under normal operations, one-through conversion is about 85vol. percent to l0l5 F.- at l0-l5 wt. percent steam dilution on feed.With the metals contamination out of the Way, the coker can be run ateven lower conversions oncethrough by higher steam dilution. The bottomsin the once-through case are retained in the gas oil. This is the reasonfor the higher Conradson carbon. In the conventional coker operationthese bottoms are cracked to extinction. The point is that even in mild,once-through coking of the present invention most of the carbon formingmaterials are deposited on the coke (feed Conradson carbon 22 wt.percent) but the severity is low enough so that the product is notnearly so much degraded to coke, gas and naphtha and fairly largequantities of 1015 R+ material are retained in the gas oil. This ispossible because the metals are left behind on the coke.

The following data show that the hydroiluoric acid treatment of residuumconverts the contaminating metal compounds to non-volatile metal solidsso that the originally volatile contaminating metals do not vapo-rizeand come overhead with the vaporous products from the ecker. The datashow that the HF treatment converts the contaminating volatile metalcompounds in the resid* ual oil into solids which subsequently aredeposited on the coke particles during the coking operation.

Bachaquero reduced crude (400 E+) was treated with 0.5 weight of 95 wt.percent HF per weight of residuum at a temperature of 250 F., a.pressure of 460 p.s.i.g. and a contact time of about minutes. In orderto show that certain metal compounds in a particular oil fraction wereconverted to a dierent `forni by the HF treatment, the untreated andtreated oils were pentane precipitated. Pentane precipitation is onlyused as a means to separate low and high molecular Weight fractions(less than and greater than 2000 mol. wt.). Metals data on the variousfractions are given in Table II. These data, show that the pentanesoluble fraction or potential vo-latile fraction 6 and the asphaltenefraction of the HF treated oil has been markedly reduced in metals withthe subsequent production of approximately l wt. percent oil insolublesolids that are concentrated in metals. The untreated oil shows highmetals for all fractions. In orde-r to demonstrate what happens tometals in the coke producing portion of the feed, the asphaltenes(Conradson carbon material) from the above solvent precipitation werecoked. Data for the various co-ker products are given in Table ill. Thegas oil fraction (650 F.-|-) obtained from the HF treated asp-haltenesshowed negligible metals while the gas oil from the untreatedasphaltenes contained excessive quantity of metals contaminants. Thislatter gas oil fraction when combined with the metals contaminantspresent in the volatile po-rtion of the untreated feed is consideredunsatisfactory for incremental catalytic cracking feed.

TABLE II Pentane Deashing of Coker Feed (3/1 Solvent/Oil) TreatedUntreated Oil Oil Pentane Soluble Fraction, Wt. Percent 83 85 MetalsAnalysis:

V, p.p.rn 5 180 Ni, p.p.n1 12 25 Asphaltene Fraction, Wt. Perccnt 15 V,p.p.1n 232 2, 400 t,p.p. 198 265 Solids, Wt. Percent 1 0 V, wt. pcrcen7.0 Ni, Wt. pereent 2. 4

TABLE III Coking of Coking of Asphaltenes Asphaltenes +Solids fromUnfrorn HF treated Oil Treat Coke Yield, Wt. percent. 50-55 45-50Inspection of Coke:

V, wt. percent 0.43 .245 Ni, wt. percent. 0. 16 .055 Sulsr, Wt. percent-3.3 3. 3 N2, Wt. percent 1. 9 1. 9 C, Wt. percen 90.1 H, wt. percent 4.9 5 on and Gas YtGe1d,(\)v.Ipereent 45-50 50-55 4., n.0 Inspections ofas i rac i 10 216 10 28 According to one form of the present invention aresidual oil feed containing between about and 600 p.p.rn. of V andbetween about 20 and 100 ppm. of Ni are treated with aqueoushydroiluoric acid as above described and the so treated residual oil ispassed directly to a fluid coking unit without the necessity of anintermediate iiltering or similar step. The hydrofluoric acid treatmentconverts the contaminating vaporous nickel and vanadium compounds to asubstantially non-volatile form which will deposit on the coke particlesto give overhead coker products having substantially no contaminatingmetal compounds therein. The solid metals are withdrawn with the excesscoke from the coker. In this way, higher gas oil yields from a Cokeroperation may tbe realizedbecause `the gas oil fractionor cut may have ahigher boiling point than when no treatment with hydrotluoric acid isused without the danger of contaminating metals carryover.

The coker overhead products in line 58 may be passed directly tocatalytic cracking unit 64 without substantially cooling of the overheadproducts to effect a heat economy and also to avoid any side reactionsor polymerization ete. of the cracked Coker vapors before they contactthe catalyst in the catalytic cracking unit 64. Or the coker overheadproducts may be fractionated to separate a gas oil fraction which iswithdrawn through line 68 for passage to the catalytic cracking unit 64and in this case there will be a smaller volume of gas and vaporspassing through the cracking unit 64. With the present invention ahigher yield of gas oil is obtained for catalytic cracking and the gasoil is substantially free from contaminating metal compounds containingnickel, vanadium or the like.

Referring now to FIG. 2 wherein the conditions of treatment aresubstantially the same as in FIG. 1 unless otherwise indicated, thereference character 100 desigL nates a line passing reduced crude or aresidual oil `to mixer vessel 101. The oil stream is mixed with freshhydrouoric acid entering through line 102 and the mixed oil and acidenter the mixing zone 101 through line 106. The mixer vessel 101 ismaintained under superatmospheric pressure. The treated oil is removedwith the acid from the mixer 101 through line 108 containing a pressurereducing valve 109 whereby the pressure on the mixture is reduced. Themixture under lreduced pressure is passed through line 110 to thehydrogen fluoride stripping vessel 112 which is operated to removehydrogen liuoride as a vapor overhead through line 114. Light naphthasuch as pentane, hexane or benzene of 1 to 10% concentration isintroduced into the lower portion of the stripper 112 through line 116-to aid in the removal of hydrogen fluoride from the oil.

Some of the hydrocarbon oil and naphtha pass overhead with the hydrogenfluoride through line 114 and this mixture is passed through thecondenser 118 to cool and condense the products and cooled mixture ispassed to settler vessel 122 where the acid and the naphtha or otherhydrocarbons are allowed to separate into two layers. The upper layercomprising naphtha is removed from the settler vessel 122 through line124 and recycled to line 116. The lower layer containing hydrogenfluoride is returned to line 106 through line 126 by compressor 127. Thetreated oil now freed of volatile metal compounds but containing metalsolids is removed from the bottom of the stripping vessel 112 throughline 128 and is processed in a coking unit which is shown as a fluidcoker.

The coking reactor 132 is operated at a temperature between about 950and 1050 F. The coker vessel contains a tluidized bed 134 of uid cokewhich is continuously circulated through line V136 to the bottom of theburner vessel 138 for heat balance and returned hot to the reactor 132through line 140 which introduces the coke into bottom portion of thereactor 132. Excess coke make is withdrawn as product through line 142from the burner 138.

The overhead coker products are Withdrawn through lines 144 and 146 andmay be cut in the overhead distillation tower 148 to any fractiondesired. Steam is preferably added to the bottom of the reactor 132through line 150 to provide fluidization gas in the bottom of thereactor. The amount of steam may vary from about to 100% weight on theoil feed. The amount of steam used determines largely the severity ofoperation, that is, the conversion of the oil feed. The reason for thisis that steam dilutes the hydrocarbons and thus reduces the oil feedpartial pressure. In once-through operation, 10% steam addition usuallyresults in 90% conversion or better, whereas 50% steam gives only about60% conversion.

Any desired fraction of the product in the distillation or fractionationtower- 148 may be recycled through line 160 by pump 162 to line 128 forrecycle to the coker reactor 132 to be coked to extinction. The recyclestream is taken ofr the tower 148 through line 160 and below the levelof product withdrawal through line 146. When coking to extinction, thecoke make is raised and the final boiling point of the product isdecreased.

The total coker overhead or the product in line 146 may be processed asin FIG. 1, that is, it may be passed directly to a catalytic crackingreactor (not shown in 8 FIG. 2) like that shown in FIG. 1 or the productfrom the coker can be fractionated to give a substantially metal freegas oil which is sent to the catalytic cracking step.

Example 1 In a specific example a West Texas vacuum residuum having aninitial boiling point of about 1050 F., an API gravity of about 11 and aConradson carbon of 20 wt. percent, is contacted with an equal weight ofby weight of aqueous hydrofluoric acid at 400 F. for one hour at apressure of about 1000 p.s.i.g. and containing 39 p.p.m of vanadium and25 p.p.m. of nickel in a mixing vessel like vessel 12. The entiremixture is passed to a settling vessel like vessel 20 to separate aliquid oil phase from an aqueous acid phase. The acid aqueous phase iswithdrawn from the bottom of the settling vessel 20 for recycle to themixing vessel 12. The oil layer which contains HF treated material insuspension or solution which does not settle out, is sent withoutfiltration or any separation or treating step directly to a coking unitlike fluid coking unit 42. The pressure in settling zone 20 is reducedto about 100 p.s.i.g.

The coking step is maintained at a temperature of about 950 F. atsubstantially atmospheric pressure. The vapor holding time in the cokingvessel is 15 seconds. The products of coking are fractionated toseparate a gas oil fraction having an end point of about 1300 F. and aConradson carbon content of 5-8 wt. percent. The gas oil contains lessthan 0.1 p.p.m. of nickel and less than 0.1 p.p.m. of vanadium. Comparedto gas oil obtained from coking the same residuum without the hydrouoricacid pretreatment and fractionated to an end point of about 1015 F. anda Conradson carbon content of 2 wt. percent, the gas oil from thepresent process invention is obtained in a 22.5% by volume greater yieldthan the gas oil from conventional coking. The gas oil from conventionalcoking contains 0.2 p.p.m. of vanadium and 0.1 p.p.m. of nickel.

Example 2 In another form of the invention, the process is modied toseparate metal contaminants from the oil feed so as to provide a stockwhich on coking will produce a demetalized gas oil feed or a wide cutoil suitable for use in catalytic cracking and also a substantiallymetal free coke which is useful in the manufacture of electrodes foraluminum manufacture. There is considerable interest in low metals cokefor use in electrode manufacture for the aluminum industry.

In this form of the invention residuum or residual oil suitable for usein a thermal cracking or coking process, but containing excessive metalcompounds such as vanadium and nickel compounds which degrade the linalcoke product, is rst demetalized by treating with anhydrous hydrogenfluoride at a temperature between about 250 F.

' and 400 F. under superatmospheric pressure between about 200 and 1000p.s.i.g. About 0.1 to 2 parts by weight of hydrogen fluoride to l partby weight of oil rnay be used. The hydrogen uoride is stripped from thetreated residual oil by a stripping gas such as a light naphtha, hexane,etc.

The treated residual oil is then thoroughly water washed to remove Watersoluble metal compounds formed by the hydrofluoric acid treatment. Thewashed residual oil is then filtered to remove any solid articles suchas coke particles that contain contaminating metal compounds.

The demetalized residual oil now contains two to three times the amountof asphaltene fraction present in the untreated residual oil feed and inthis way an increase in coke make is made possible. The coke may beproduced by a fluid or delayed or any conventional coking process. Thedemetalized treated residual oil may be separated into an asphaltenefraction and deasphalted oil by conventional precipitation steps priorto the coking step and the deasphalted residual oil can be used incatalytic cracking or as a low metals fuel oil.

In a specific example a residual oil such as one having an initialboiling point of about 400 F., an API gravity of about 14.5 and aConradson carbon of about 10.7 Wt. percent is mixed with l part byWeight of 4anhydrous hydrofiuoric acid per part by weight of residualoil at 300 F. at a pressure of about 800 p.s.i.g. in a mixing Vessel forabout 60 minutes.

The hydrofiuoric acid is then stripped from the residual by treatmentwith a stripping gas such as a light naphtha. Other stripping gases suchas pentane, hexane, benzene, etc. may be used. The stripped residual oilis then thor oughly water washed with tap water to remove water solublemetal compounds formed as a result of the hydrofluoric acid treatment.About 3 parts by weight of Water to one part by weight of treated oil isused. Following the Water washing step, the treated oil is filtered bypassing through a 200 mesh filter to remove any solids and cokeparticles which contain the objectionable metal compounds. The residualoil contains about 18 p.p.m. of vanadium and about 22 p.p.m. of nickel.

The filtered residual oil now contains about three times the amount ofthe asphaltene fraction present in the untreated residual oil. Thefiltered oil is then coked in the same way as done in Example l toobtain a gas oil fraction boiling up to about 1015 F. and having aConradson carbon of about 1 to 2 wt. percent. The gas oil contains lessthan about 1 p.p.m. of vanadium and less than about l p.p.m. of nickel.The coke yield is about 30% of residual oil feed and the coke containsabout 60 p.p.m. of vanadium and 70 p.p.m. of nickel. The coke yield isgreater than that obtained in conventional iiuid coking by about 300% byweight. Cokes and/or oils containing less vanadium and nickel can beobtained by the same procedure from feedstocks which have lowerconcentrations of the same metals.

In a further modification the treated residual oil may be treated at atemperature of about 170 F. with a precipitating agent such as propaneusing about 4 parts by weight of propane to one part by weight of thetreated demetalized residual oil. The pressure is about 450 p.s.i.g. Thedemetalized asphaltene fraction is separated prior to the coking step.After coking this asphaltene fraction, the resulting coke has a vanadiumcontent of about 60 ppm. and a nickel content of about 70 p.p.m. Thedeasphalted oil is suitable as a catalytic cracking feedstock. Insteadof propane other precipitating agents such as butane, pentane, hexane,heptane or mixtures thereof may be used. The temperature of theprecipitating treatment may vary between about 100 F. and 300 F. Thepressure for the precipitating treatment may be between about 100p.s.i.g. and 500 p.s.i.g.

What is claimed is:

l. A process for converting high boiling hydrocarbons containingcracking catalyst contaminating materials which comprises treating in acontacting zone such a high boiling hydrocarbon fraction with hydrogenfluoride at an elevated temperature, separating an oil phasesubstantially free of hydrogen fluoride, passing said oil phase directlyWithout filtration to a coking zone to crack said treated hydrocarbonfraction to vaporous reaction products and coke, and recovering a gasoil fraction from said vaporous reaction products in increased yield andsub stantially free of catalyst contaminating metals.

2. A process according to claim l wherein said hydrofiuoric acid is inan aqueous solution.

3. A process according to claim l wherein said hydrofluoric acid is inanhydrous form.

4. A process according to claim l wherein said coking process is a fluidcoking process.

5. A process for converting high boiling hydrocarbons which cannot bedistilled under normal temperature and pressure conditions withoutcracking and which contain catalyst contaminating materials whichcomprises treating in a contacting zone such a high boiling hydrocarbonfraction with an aqueous hydrouoric acid solution at an elevatedtemperature, separating an oil phase from an aqueous phase, passing saidoil phase directly without iiltration to a fiuid coking zone to cracksaid treated hydrocarbon fraction to vaporous reaction products andcoke, passing said vaporous reaction products with areduced amount ofcatalyst contaminating metals directly to a catalytic cracking zone andrecovering desired products from the resulting catalytically crackedproducts.-

6. A process for converting high boiling hydrocarbons which cannot bedistilled under normal temperature and pressure conditions withoutcracking and which contain catalyst contaminating materials whichcomprises treating in a contacting zone such a high boiling hydrocarbonfraction with an aqueous hydrouoric acid'solution at an elevatedtemperature, separating an oil phase Afrom an aqueous phase, rpassingsaid oil phase directly without filtration to a fluid coking zone tocrack said treated hydrocarbon fraction to vaporous reaction productsand coke, passing said vaporous reaction products to a fractionatingzone to separate and recover a gas oil fraction substantially free ofcatalyst contaminating materials, passing said recovered gas oilfraction to a catalytic cracking unit, and recovering desired productsfrom the catalytically cracked products.

7. A process for converting high boiling hydrocarbons which cannot bedistilled under normal temperature and pressure conditions withoutcracking and which contain catalyst contaminating materials Whichcomprises treating in a contacting zone such a high boiling hydrocarbonfraction with an aqueous hydrofiuoric acid solution of a concentrationgreater than about 50% by weight of HF at a temperature between about100 F. and 700 F. and using about 0.1 to 2 weights of the hydrofiuoricacid solution per weight of the hydrocarbon fraction to be treated,maintaining the contacting time in said contacting zone between about 2and 120 minutes and the pressure between about l00 and 1800 p.s.i.g., orat a pressure suliicient to maintain the hydrofiuoric acid in the liquidphase, separating an oil phase from an acid phase, passing said oilphase, freed of HF without any solids separation step to a coking zonecontaining a bed of coke particles to crack said treated hydrocarbonfraction to vaporous reaction products with a reduced amount of catalystcontaminating metals, and coke which contains the catalyst contaminatingmaterial deposited on the coke particles of said bed,and recovering agas oil fraction from said vaporous cracked products containing lessthan l p.p.m. of vanadium or nickel contaminating materials.

8. A process according to claim 7 wherein the concentration of theaqueous hydrofiuoric acid is between about and 100% by weight, thetemperature in said contacting zone is between about F. and 300 F., theweight ratio of aqueous hydrofluoric acid to oil feed is between about0.12 and 3.5 and the time of contacting is between about 2.0 and 13minutes.

9. A process for converting high boiling hydrocarbons which containcracking catalyst contaminating materials which comprises treating in acontacting Zone such a high boiling hydrocarbon fraction with anhydroushydrogen iiuoride at an elevated temperature and pressure, strippinghydrogen fluoride from said treated hydrocarbon fraction, water Washingthe treated and stripped hydrocarbon fraction to remove water solublemetal compounds, then filtering the treated and washed hydrocarbonfraction to remove solids, then coking the treated hydrocarbon fractionto obtain coke having less than about 60 p.p.m. of vanadium and 70 ppm.of nickel depending on the feedstock and a gas oil suitable for use as acatalytic cracking lfeedstock and containing less than about 0.5 p.p.m.of vanadium and 0.2 p.p.m. of nickel.

10. A process according to claim 9 wherein the treated and washedhydrocarbon fraction is treated with a low 11 boiling paran hydrocarbonto separate an asphaltene fraction from a deasphalted oil and cokingsaid asphaltene fraction to obtain a low metals coke.

1l. A process according to claim 9 wherein the treatment with anhydroushydrogen uoride is at a temperature between about 250 F. and 450 F.

12. A process for converting high boiling hydrocarbons which cannot bedistilled under normal temperature and pressure conditions withoutcracking and which contain catalyst contaminating materials whichcomprises treating in a contacting zone such a high boiling hydrocarbonfraction with an aqueous hydrouoric acid solution of a concentrationgreater than about 50% by weight of HF at a temperature between about100 F. and 700 F. and using about 0.1 to 2 weights of the hydrouoric lacid solution per weight of the hydrocarbon fraction to be treated,maintaining the contacting time in said contacting zone between about 2and 120 minutes and the pressure sufficient to maintain the hydrofluoricacid in the liquid phase, separating an oil phase from an acid phase,passing said oil phase, freed of HF without any solids separation stepto a coking zone containing a bed of coke particles to crack saidtreated hydrocarbon fraction to vaporous reaction products with areduced amount of catalyst contaminating metals, and coke which containsthe catalyst contaminating material deposited on the coke particles ofsaid bed, passing the total overhead vaporous reaction products withoutsubstantial cooling to a catalytic cracking zone and recovering desiredproducts from said catalytically cracked products.

References Cited in the tile of this patent UNITED STATES PATENTS2,525,812 Lien et al. Oct. 17, 1950 2,677,648 Lien et al. May 4, 19542,868,715 Jahnig et al. Ian. 13, 1959 2,906,690 Brown Sept. 29, 1959

1. A PROCESS FOR CONVERTING HIGH BOILING HYDROCARBONS CONTAININGCRACKING CATALYST CONTAMINATING MATERIALS WHICH COMPRISES TREATING IN ACONTACTING ZONE SUCH A HIGH BOILING HYDROCARBON FRACTION WITH HYDROGENFLUORIDE AT AN ELEVATED TEMPERATURE, SEPARATING AN OIL PHASESUBSTANTIALLY FREE OF HYDROGEN FLOURIDE, PASSING SAID OIL PHASE DIRECTLYWITHOUT FILTRATION TO A COKING ZONE TO CRACK SAID